1. Field of the Invention
The present invention relates to an optical system for optically reading information from and writing information onto an optical recording medium.
2. Description of the Related Art
Optical reading and writing systems such as a near field optical disk drive read information from and write information onto an optical recording medium, such as an optical disk, using an optical pickup. An optical reading and writing system includes an actuator driving over an optical disk while being supported by a spindle motor. An example of an optical reading and writing system employing such an actuator is shown in FIGS. 1 and 2.
Referring to FIGS. 1 and 2, an actuator 2 for driving an actuator arm 4 is mounted to a base 1 enabling the actuator 2 to pivot relative to the base 1. An optical disk 7 is rotatably mounted onto a spindle motor 6, and an optical pickup is installed on the actuator 2 to be capable of reading information from and writing information onto the optical disk 7 by focusing a light beam L onto the optical disk 7. The first portion of the optical pickup is formed at a mounter 3, which is the pivot portion of the actuator 2. The optical pickup includes a light source 10 for emitting light, an objective lens 11 near the end of a slider 9, and a photodetector 13 installed in the mounter 3. A flexible load beam 8 is attached to the actuator arm 4 to be separated a predetermined distance from the lower side of an end of the arm 4. The slider 9 is installed at the free end of the load beam 8. The slider 9 levitates over the optical disk 7 by hydrodynamics during rotation of the optical disk 7, thereby forming a so-called near field.
During a reading or writing operation, the actuator arm 4 pivots by the driving force of a voice coil motor 5 in the radial direction A of the optical disk 7. Here, the light beam L emitted from the light source 10 is reflected by a reflection member 15 mounted at the end of the actuator arm 4, and incident into the objective lens 11. The objective lens 11 focuses the incident beam L to form a light spot on the recording surface of the optical disk 7. In turn, the light beam is reflected from the recording surface of the optical disk 7 and passes through the objective lens 11 and the reflection member 15. An optical path changing member 17 arranged on the optical path reflects the light reflected by the reflection member 15 back toward the photodetector 13. The photodetector 13 receives the incident light and detects information.
In the structure having the above configuration, however, after the light beam emitted from the light source 10 is incident onto the recording surface of the optical disk 7, the light beam reflected from the recording surface is detected by the photodetector 13 via the same optical path but in the opposite direction. As the light beam travels along the optical path, the light beam contacts air, and there is some loss in the light beam. In particular, because the recording surface of the optical disk 7 is separated a predetermined distance apart from the photodetector 13, the optical loss increases with reduced reliability of information written to or read from the optical disk 7. Therefore, there is a need for a mechanism to help decrease optical loss and increase reliability of information written to and/or read from the optical disk 7.
There is an ever increasing need for optical disks having a high memory capacity, and the recording density of optical disks is increasing. For this reason, there is also a need for a new mechanism capable of precisely driving a slider to form a light spot on a desired spot of the recording surface. More precisely, the actuator 2 driven by a large driving force of the voice coil motor 5 has a limitation in accurately controlling the slider 9 fixed to the load beam 8 that is flexible.